Adamantanes are useful for intermediates of various chemicals such as lubricants and medicines. For producing such adamantanes, generally employed is a method of isomerizing tricyclic saturated hydrocarbons having at least 10 carbon atoms each. For the isomerization, used is aluminium chloride for the catalyst.
However, in the method of using aluminium chloride for the catalyst for the isomerization, a large amount of aluminium chloride must be used relative to the starting compound. In addition, in the method, the aluminium chloride catalyst forms a complex with a heavy component during the isomerization, and therefore it cannot be recycled. Accordingly, the method gives a large amount of aluminium waste and its serious problem is that the aluminium waste to be processed for its disposal has some negative influence on the natural environment. Another problem with the method is that the aluminium chloride catalyst used discolors the adamantanes produced therein, and therefore the method requires recrystallization of the products or decoloration thereof with activated charcoal, but the post-treatment is troublesome.
In JP-B 52-2909 and 53-35944, proposed is a method of using a catalyst of various active metals such as platinum, rhenium, nickel or cobalt carried by cation-exchanged zeolite, for that isomerization. In the method, however, since the yield of adamantanes produced through isomerization using the metal-carrying catalyst is low, hydrogen chloride is used along therewith for increasing the yield of the adamantanes. Therefore, there is disadvantage in that a production apparatus made of an expensive corrosion-resistant material must be used in this method.
Given that situation, it is desired to develop a method of selectively producing adamantanes in a production apparatus made of an inexpensive material, not having any negative influence on the natural environment.
The object of the present invention is to provide a method of selectively producing adamantanes in a production apparatus made of an inexpensive material, not having any negative influence on the natural environment.